Direction-sensitive displacement analysis by multiple frequency holographic interferometry

A method for determining the directions of displacement in double exposure holographic interferometry is described. The technique requires the use of different frequencies in each of the two holographic exposures and thus can be thought of as a combination of conventional multifrequency contouring and holographic interferometry. The necessary equations to describe the resulting fringe pattern are developed. Two deformation fields, one theoretical and one experimental, are used to illustrate the phenomena. The experimental deformation was the result of a Rayleigh surface wave propagating in a rock specimen. The holograms were obtained with a Q-switched, multifrequency pulsed ruby laser.